Vehicle tire and tread therefor



March 21,1950 c. L. BEWARE 2,501

VEHICLE TIRE AND TREAD THEREFOR Original Filed Feb. 2, 1942 r 1 I r I II 4 I p I u I I I I I I I I 1 I r I I a I v p I I I 1 I I a r a a p I II p l I J i I I l I I p l I p r I I I I I I i 1 r Chalmer Beward ATTORNEYS Patented Mar. 21, 1950 i UNITED vs ires PATENT OFFICE VEHICLE. TIREAND TREAD THEREFOR;

Chalmer L. Reward, Akron, Ohio, assignor to The General Tire & RubberCompany, Akron, Ohio, a corporation. oi Ohio Original applicationFebruary 2, 1942, Serial No. 429,140, Divided and this applicationAugust 23,1944, Serial No.- 550,718 V 1 Claims. (01. 152M354) 1 z v 2 7Tbs application is a division of my copending ing increased interracialarea between the vulapplication Serial No. 429,140, filed February 2,canized compoundsof the tread and side wall 1942, which has matured intoPatent 2,437,878 portions. March 16, 1948. The invention relates tovehicle Other objects will be apparent from the fOH-OW! tires and tocomposite tread and side wall strips 5 ing detailed description of theinvention as evie for application to tire carcasses one building dencedby the accompanying drawings, in which: dr Figure l'ls a diagrammaticside elevational In usual practice, the tread and outer side walls viewof apparatus which maybe used in producoi a tire are formed'of a singlestrip of rubber ing composite strips of the present invention; compoundwhich is cut to the proper length, Fig. 2 is a sectional view on theline 2-.-2 of applied upon and vulcanized to the fabric can Fig; 1;

cass of the tire. The rubber compound from Fig. 3 is a sectional view onthe line 3w3 of which the wear-resistant tread portion of the tire Fig.1;

is formed should have a relatively heavy loading. Fig. 4 is a top planview of a portion of the apof carbon black to increase its wearingproperparatus seen from lines 44 of Fig. 1, showing ties. The coveringfor the side wall portions of. the two rubber compounds used in formingthe the tire, however, are preferably .of a softer, more composite stripat the moment of their union; elastic rubber compound to provideincreased re- Fig. 5 is a sectional view through a composite sistance toflex-cracking. Also, a softer rubber tread and side wall strip embodyingthe present adjacent the tire carcass provides better adhesion g0invention; and

to the carcass. Fig. 6 is asectional view through a portion ofHeretoiore, it has been proposed to form the atire embodying the presentinvention.

composite tread and side wall strips .of two dif- Referring to thedrawing, and more partied.-

ferent rubber compositions, withthe medial relalarly to Fig. 5,composite strips of the present tively thick body portion of the stripfrom which invention have a central: tread portion a of rela t t d inthe finished article is .to be formed. tively highly loadedweanresistant rubber come. of a relatively hard composition and with thepound nd a base portion b, pref rably'of more relatively thin side.margins of the strip, which. flexible and of relativelysofter rubbercompound. are adapted in the finished article to form the The treadstrip has greater width than height, the side walls of the tire, .ofa-softercomposition. Width about C rr p nding to the tread of. the

In the manufacture of .composite treadandside tire to be formed. It mayhave a rectangular wall strips heretofore proposedthe base of the crosssection .or, preferaby, a trapezoidal cross-J composite strip,consisting .of the marginal porsection with relatively sharp edges, thelower face tions for formation of the sidewalls and an inbeing'widerthan the upper face.

termediate connecting web portion, is preformed he base portion 1)comprises mar inal p in substantially the shape desired in the finalartie tons I adapted to form. the covering for the side.

cle so that itwill receive a. separately preformed wall of the;completed tire; The marginal p.01..- tread strip without appreciabledeformation. tions are. connected by a central web. portion .2,

Composite strips formed in this manner, wherein which serves to connectthe tread portion a. with there is an abrupt juncture between therelatively 4Q the tire carcass. -.The marginal portions 1 are hard treadstrip and the softer-marginal portions, usually relatively. thin. at.their outer edges and are undesirable for the reason that concentrationincrease in thickness towards the center of the,

of stress is likely to occur at this abrupt. juncstrip, with maximumthickness reached in longiture to causecracking andseparation of thetread tudinal ridges 3,1 the nejg'hbgrhpod Qf t June.

portion from the de Wal portion f the-finished ture of the-marginalportions withthe tread p01,.

article. tion. The ridges 3.: are positioned in th It is therefore anobject .of the present invenposits tread so thatwhen the tread isapplied to tion to provide a composite tread and side wall the thecarcass they will lie intheshoulder por strip having a relatlv lylhard,W r-resistant metions of th ire. The web portion 2 preferably dialportion and a softer base portion wherein 5( falls away in thicknessfrom the ridges .3 to pro? there is no abrupt terminationoi the medialtread vide a cha ne n wh ch the major portion of the portionintothemarsinalbase 11 111 1011. strip a is carriedto form the treadportion a of It is a still im her obiect. to provide a tire thecomposite strip. The tread portion a over.-. having a. hard,wear-resistant tread and so t s and is s r g b nded to the web portionside, wall covcrinssconuected .by a weband hav- 55. of thebaseb betweenthe ridges 3.

According to the present invention, the tread portion has marginal edgeportions which are preferably tapered and overlie the ridges 3, so thatwhen the composite strip is molded in a tire, the wear-resistant treadcompound of the edge portions 5 extends beyond the shoulder and partwayup the side wall of the tire. The interface between the rubber compoundof the tread portion a and the rubber compound of the base 12 preferablyis uneven or contains undulations as when the compounds were subject toflow after contact. The undulations or roughness of the surface providelarger interfacial area between the compounds of the tread portion a andthe base b than when both the tread portion and the base are separatelyformed to final shape with smooth surfaces and simply pressed together.The undulations in the tread and base portions are complemental as whenthe tread strip is united to the base strip under calendering pressureand under conditions of turbulence in accordance with the methodhereinafter set forth.

Referring particularly to Figs. 1 to 4, inclusive, suitable apparatusfor forming the composite treads of the present invention may comprisemeans for forming the tread strip a in the desired shape, means such ascoacting rolls in a suitable calender for forming a rubber compound intoa relatively fiat strip having greater width than the tread strip, andmeans including a contour roll and a backing roll for shaping the rubberof the flat strip into the form it occupies in the base portion of thecomposite strip and for substantially simultaneously uniting thepreformed tread portion a thereto under calender pressure and preferablyunder conditions of turbulence or flow, in at least one rubber compoundforming the composite strip.

The calender preferably used is of the four-roll contour type, havingrolls A, B, C and D arranged in conventional manner. One calender roll,D, is shaped to substantially the contour desired for the upper surfaceof a composite strip suitable for application on a drum to a tirecarcass. The rolls A, B and C, the latter serving as a backing roll forthe contour roll D, may be of conventional cylindrical form,

The tread strip is formed from the bank of rubber 34 supplied to thebight between rolls A and B. The roll A preferably has greater speedthan has intermediate roll B and the sheeted tread compound 35 iscarried over the top of the roll A, where it is trimmed or skived tosuitable width and shape by the trimmer 36. The stock 31 trimmed fromthe edges of the strip a is returned to the bank of rubber 34. The basestrip 12 of sheeted flexible compound for forming the base I) of thecomposite tread is formed from the bank 38 by the interaction of therolls B and C. The speed of rolls C and D is approximately equal andgreater than the speed of intermediate roll B. The speed of the upperroll A is preferably somewhat less than that of rolls C and D tocompensate for the stretch imparted in the strip a by the roll 29 whichcooperates with the roll D. Since the usual calender is several timeswider than the width of the composite strip, separating blocks may beinterposed between portions of the rolls so that a single pair of rollsmay serve both to' calender and to Warm-up the supply of rubber compoundfor bank 34 or 38, if desired.

The contour roll D may have cylindrical end portions and an intermediateformed portion between suitable stops of the width desired for thecomposite tread and side wall strips of the present invention. Theformed portion has an annular groove or channel, preferably havingconvexlike or rounded annular bottom face 18 and outwardly incliningsides IS. The channel 28 is suitably shaped to receive the preformedtread strip a. The diameter of the roll D preferably is smallest at thejuncture of the base 18 with the sides IQ of the channel and becomesprogressively larger until the maximum diameter of the cylindricalportion [5 is reached. The opening between the coacting rolls C and Dcorresponds substantially to the cross section of the desired compositestrip taking into account the elasticity of the compound. The stops 20provided in the bight between rolls C and D decrease the tendency forflow of rubber toward the end of the rolls; the distance between thestops 20 may be adjusted to equal or exceed the overall width desired inthe composite strip. If the calendered width of the composite strip isgreater than desired, suitable trimmers knot shown) may be provided totrim excess flexible stock from the outer edges of the marginal portions1.

In the formation of composite strips embody ing the present invention,the base portion and the tread portion are united under calenderpressure. Rubber compound of a type suitable for forming the side wallportion of the composite strip may be continuously fed from a suitablesource, not shown, such as a warm-up mill, into the bight and betweenthe intermediate and lower rolls B and C, respectively. The amount ofrub-- ber in the bight is sufficient to provide a suitable bank 38 andthe rubber compound emerging from between the rolls B and C may be inthe form of a flat sheet [2 having substantially the average thicknessof the base portion b of the opposite strip, so that the small bank ofrubber formed;

by operation of rolls C and D remains of substantially constant size.The thickness of the relatively flat base strip I2 is greater than thethickness of the edge portions of the marginal,

portions l of the composite strip, so that when the compound of thestrip l2 passes between the contour roll D and the backing roll C thesmall bank 21 of the compound 12 is formed and a flow of the compound 12toward'the medial portion of the contour roll D takes place to assist informing the longitudinal ridges 3 and to cause turbulence at theinterface between the tread strip a and the base portion b.

Means is provided for feeding or incorporating the preformed tread stripa into the annular channel of the contour roll with its narrower orupper face 28 in contact with the bottom curved portion N3 of thechannel and for applying tension thereto to cause it to conform'to theshape of the groove. This means may comprise a suitable tension roll 29which is rotatably carried in suitable slides and is adapted to ride onthe roll D. The preformed tread strip a from the roll A is passed underroll 29 and over the roll D, and by the tension due to the drag of theroll' 29 it is pulled into the channel H and into conformity with therounded base l3 thereof. The tread strip a. in the channel on the roll Dis carried into contact with the sheeted rubber com-" pound 12 on theroll C and united thereto under calendering pressure. Probably due tothe fact' that the outer medial portion 32 (Fig. 3) of the strip a onthe roll D travelsat a somewhat greater speed' than the marginalportions of the strip a, due to the larger diameter of the base of thechannel 28 at its medial portion, there appears to be'a somewhat higherpressure on the medial portion of the strip it than at its edges. Thisdifferential pressure or differential in flow resistance causes flow ofthe compound thereof toward the end portions and beyond. The flow of thecompound from the strip :1 towards the ends of the roll D meeting withthe opposite flow of the rubher from the bank 2'! toward the axis ormedial portion of the composite strip apparently causes some turbulenceat the interface between the strips a and b with the result that the twocompounds are worked-together so that a wavy interface and excellentadhesion are obtained.

When the tread strip and the base are united in this manner, it has beenfound that the flow of the flexible compound I2 from the bank 21automatically provides the desired ridges 3 at the shoulder portions ofthe composite tread. It has also been found that when the preformedstrip a. is united to the base 12 in this manner, the compound of thepreformed strip a flows laterally along the contour roll to providetapered edges which overlie or tend to overlie the. ridges 3 of the baseportion, thus preventing abrupt termination of the medial tread portiona.

Because of the turbulence of the bank 21 and the flow of the compound inthe strip a, undulations are produced over the major portion of theinterface between the tread'portion a and the base portion I). Theseundulations further alleviate any tendency of separation of the treadfrom the side wall stock of the tires produced.

Referring particularly to Fig. 6, the tires embodying the presentinvention may comprise a carcass of conventional form having a number ofplies of stretch-resistant elements extending between the beads, thestretch-resistant elements in alternate plies being substantiallyparallel and at an angle to those in adjacent plies as in conventionaltires. When the composite strip illustrated in Fig. 5 is suitablyincorporated in the tire, it is seen that the side wall rubber compoundI of the side wall covering extends continuously over the crown of thetire from adjacent the beads. The relatively thick ridges 3 in which theside walls terminate form a thickened shoulder adjacent the edges of theroad-contacting surface thereof. The wear-resistant tread compound awhich forms the tread of the tire extends over the shoulders with theinterface and the marginal portions 5 extending partly up onto the sidewalls to provide extra protection for the side walls adjacent theshoulder.

Furthermore, it is to be understood that the particular form of productshown and described and the particular procedure set forth are presentedfor purposes of explanation and illustration and that variousmodifications of said product and procedure can be made withoutdeparting from my invention as defined in the appended claims.

What I claim is:

l. A composite strip for forming the tread and side wall coverings of avehicle tire, comprising a central tread portion of a wear-resistantrubber compound and a base portion of a second and different rubbercompound, said base portion having marginal portions for forming theside wall coverings of a tire, one marginal portion extending beyondeach side edge of said tread portion and being relatively thin at itsouter edges, the inner edge of each marginal portion term nating in alongitudinal ridge, and a central web portion underlying said treadportion and connecting said marginal portions through said longitudinal-ridges, said tread portion overlying said web-portion and havingmarginal edge pore tions which overlie said ridges and part ofisaidmarginal portions, side-portions of the. interface between said treadand base portions having all the characteristics of interfaces betweencom,- pounds identical to those of said tread and base portions whichare forced together under pressure, while portions of at least one ofsaid come pounds first contacting the other compound are in the state ofthe turbulent flow of a bank of rubberlike material between spacedportions of pressure rolls.

2. A composite'strip for forming the tread and side wall coverings of avehicle tire, comprising a central tread portion of a wear-resistantrubber compound and a base portion of a second and different rubbercompound, said base portion having marginal portions for formin the sidewall coverings of a tire, one marginal portion extending beyond eachside edge of said tread portion and being relatively thin at its outeredges, the inner edge of each marginal portion term-inating in alongitudinal ridge, and a central web portion underlying said treadportion and connecting said marginal portions through said longitudinalridges, said tread portion overlying said web portion and having taperedmarginal edge portions which overlie said ridges and part .of said marinal portions, the width of the interface be? tween saidtread portionand said base portion being greater thanthe width of the bondedface ofthe tread portion as separately formed, side portions of the interfacebetween said tread and base portions having all the characteristics ofinterfaces between compounds identical to those of said tread and baseportions which are forced together under pressure, while portions of atleast one of said compounds first contacting the other compound are inthe state of the turbulent flow of a bank of rubberlike material betweenspaced portions of pressure rolls.

3. A composite strip for forming the tread and side wall coverings of avehicle tire, comprising a central tread portion of a wear-resistantrubber compound and a base portion of a second and different rubbercompound, said base portion having marginal portions for forming theside wall coverings of a tire, one marginal portion extending beyondeach side edge of said tread portion and being relatively thin at itsouter edges, the inner edge of each marginal portion terminating in alongitudinal ridge, and a central web portion underlying said treadportion and connecting said marginal portions through said longitudinalridges, said tread portion overlying said web portion and having taperedmarginal edge portions which overlie said ridges and part of saidmarginal portions, side portions of the interface between said tread andbase portions having all the characteristics of interfaces betweencompounds identical to those of said tread and base portions which areforced together under pressure, while portions of at least one of saidcompounds first contacting the other compound are in the state of theturbulent flow of a bank of rubberlike material between spaced portionsof pressure rolls.

4. A pneumatic vehicle tire comprising a tire carcass containingstretch-resisting elements extending between substantially inextensiblebeads, side wall coverings of a suitable flex-resisting rubber compoundand a tread or road-contacting portion of another and difierent rubbercompound, the rubber compound of said side wall Eov'ei'ing's extendingsubstantially from bead to bead, one edge of each side wall terminatingadjacent an edge of the road-contactin surface in a shoulder containinga thickened ridge of substantially the same compound as said side wall,a web of the side wall compound connecting the ridges of said shouldersand underlying said tread portion, portions of said tread portion beingbonded to said underlying web portion and to said ridges, the interfacebetween the compound of said tread portion and said side wall compoundextending over said shoulder and partway up said side walls, sideportions of the interface between said tread and base portions havingall the characteristics of interfaces between compounds identical tothose of said tread and base portions which are forced together underpressure, while portions of at least one of said compounds firstcontacting the other compound are in the state of the turbulent flow ofa bank of rubberlike material between spaced portions of pressure rolls.

5. A pneumatic vehicle tire comprising a tire carcass containingstretch-resisting elements extending between substantially inextensiblebeads,

side wall coverings of a suitable flex-resisting rubber compound and atread or road-contacting portion of another and difierent rubbercompound, the rubber compound of said side wall coverings extendinsubstantially from bead to bead, one edge of each side wall terminatingadjacent an edge of the road-contacting surface in a shoulder containinga thickened ridge of sub- Number Name Date Re.22,080 Bowers Apr. 29, 1942 1,268,437 Ciough June 4, 1918 1,276,875 Colby Aug. 27, 1918 1,352,164Yelm Sept. 7, 1920 1,357,098 Kryder Oct. 26, 1920 1,403,058 Pushee Jan.10, 1922 1,954,926 Fraser Apr. 17, 1934 2,177,165 Beckman Oct. 24, 19392,228,212 Heintz Jan. '1, 1941' 2,232,488 Smith Feb. 18, 1941"stantially the same compound as said side wall; a web. of the side wallcompound connecting the ridges of said shoulders and underlying saidtread portion, said tread portion overlying said web and saidsthickenedridges of said shoulders, and side portions of the interface betweensaid treadand base portions having all the characteristics of interiacesbetween compounds identical to those or said tread and base portionswhich are forced together under pressure, while portions of at least}one of said compounds first contacting the othericompound are in thestate of the turbulent fiQWfOf a bank of rubberlike material betweenspaced portions of pressure rolls.

' CHALMER L. BEWARD.

REFERENCES CITED UNITED STATES PATIENTS

